Table 1. Changes to ocean chemistry and pH estimated using the OCMIP3 models calculated from surface ocean
measurements and our understanding of ocean chemistry. Note that the concentration of bicarbonate ion (HCO3
–
) and
carbonic acid (H2CO3) increase with rising atmospheric concentration of CO2 while carbonate ion (CO3
2–) decreases. The
average pH of the surface ocean waters decreases with increasing atmospheric CO2 concentration. (Assumptions used
in model: Total alkalinity = 2324 mol/kg, temperature = 18° C. All other assumptions as per OCMIP3 (Institut Pierre
Simon Laplace 2005). Aragonite and calcite saturation calculated as per Mucci & Morse (1990). Physical oceanographic
modelling is based on Bryan (1969) and Cox (1984). | If CO2 emissions continue on current trends, this could
result in the average pH of the surface oceans
decreasing by 0.5 units below the level in pre-industrial
times, by 2100. This is beyond the range of natural
variability and represents a level probably not
experienced for at least hundreds of thousands of years
and possibly much longer (Caldeira & Wickett 2003).
Critically, the rate of change is also at least 100 times
higher than the maximum rate observed during this time
period. These changes are so rapid that they will
significantly reduce the buffering capacity of the natural
processes that have moderated changes in ocean
chemistry over most of geological time. |